Speed Converter
Convert km/h, mph, m/s and knots.
Was this tool helpful?
Thanks for the feedback!
The Speed Converter changes a speed between kilometres per hour, miles per hour, metres per second and knots. It is useful for comparing bowling speeds quoted in km/h and mph, solving school physics problems that want m/s, and reading the knots used in aviation, shipping and cyclone warnings.
Using the converter
Enter the number in Value, set From to the unit it is in and To to the unit you need, then press Convert. Internally everything is expressed in km/h: one mph is 1.609344 km/h, one m/s is 3.6 km/h and one knot is 1.852 km/h. The result line shows the target unit, and the list below gives the other three at once, to six decimal places.
Worked example: a 150 km/h delivery
Indian broadcasts show fast bowling in km/h, while some overseas coverage uses mph. Enter 150 From km/h To mph:
150 ÷ 1.609344 = 93.205679 mph
The same ball is 41.666667 m/s (150 ÷ 3.6) and 80.993521 knots (150 ÷ 1.852).
The 5/18 shortcut from school
Because one m/s is 3.6 km/h, Indian textbooks teach multiplying km/h by 5/18 to get m/s, and m/s by 18/5 to go back. For example, 72 km/h × 5/18 = 20 m/s, which is exactly what the converter returns. The same factor helps with weather apps that report wind in metres per second: a 10 m/s wind is 36 km/h, enough to set small trees swaying.
Knots and cyclone warnings
A knot is one nautical mile (1,852 m) per hour. The India Meteorological Department grades cyclonic disturbances by maximum sustained wind speed in knots:
| IMD category | Wind speed (knots) |
|---|---|
| Depression | 17 to 27 |
| Deep depression | 28 to 33 |
| Cyclonic storm | 34 to 47 |
| Severe cyclonic storm | 48 to 63 |
| Very severe cyclonic storm | 64 to 89 |
| Extremely severe cyclonic storm | 90 to 119 |
| Super cyclonic storm | 120 and above |
Entering 34 knots shows that the cyclonic storm threshold is 62.968 km/h, or about 39 mph. Knots also appear in flight information: an airliner cruising at 450 knots is covering 833.4 km every hour.
What it does not cover
- Running pace. Minutes per kilometre is the inverse of speed, so it cannot be reached by a simple multiplication. The running pace calculator handles that.
- Distance or travel time. To work out how long a 300 km drive takes at a given speed, use the speed, distance and time calculator.
- Other units. Feet per second and Mach numbers are not included. Mach depends on the speed of sound, which changes with air temperature, so it has no single conversion factor.